I could say: "we only notice those times and remember them, not the dozens of times a day it doesn't happen"... but that's not totally accurate.. as I drive around, there are certain crossroads where it seems there's always another car that arrives about the same time.. yes, these are 'main traffic roads' into town or between towns 10-20 mi apart.. but that's only a few dozen to a hundred cars daily as my county is fifth largest in CA (sq mi)[about 6,300 sq mi] but only 39K-42K population.. and 90% of traffic uses Interstate 5 which bisects county or another two-lane State highway that takes one NE into Oregon.. so why do two of us meet? we wave and move on.. I'm not 'startled' to see someone at crossroads.. I'm EXPECTING THEM.. sometimes we even know each other; yet not by name..